The invention relates to multi-material assemblies through which light is propagated, and more particularly to waveguides.
Polarization dependent loss (PDL) in a waveguide is caused by the difference of propagation losses between vertically polarized (TM) and horizontally polarized (TE) light waves. Typically, TM light has higher propagation loss than TE light. When a light wave passes through a boundary between two optical materials of different refractive indices, the reflection loss at the boundary also depends on the polarization.
For optical waveguide devices with metal electrodes above and/or below the waveguide, a conventional method of reducing the PDL of a device is to increase the thickness of a buffer layer between the waveguide and an electrode. A thicker buffer layer may cause the device to have a higher operating voltage, which is not desirable. Therefore, a need exists for a waveguide having a reduced PDL while substantially maintaining or reducing its operating voltage.
The invention includes a multi-material structure comprising at least two components through which light is propagated. The components are of different materials and are joined at an end surface of each. The end surfaces are at angles other than normal to the direction of light propagation. A device having the multi-material structure has a polarization dependent loss less than if the components had end surfaces normal to the direction of light propagation. Embodiments of the invention are particularly applicable to a waveguide substrate/optical fiber interface.
Also included is a method of reducing polarization dependent loss between joined components through which light is propagated.